Jamaica, island nation, third-largest island of the Greater Antilles, situated south of Cuba in the northern Caribbean Sea. Jamaica has a maximum length, from east to west, of about 235 km (146 mi); the maximum width is around 80 km (50 mi). The total area of the nation is 10,991 sq km (4,244 sq mi). Kingston is the capital and largest city of Jamaica, and also a large commercial seaport.